TEHRAN, Iran -- In a bid to ease international concerns over its nuclear program, Iran has converted more than a third of its most highly enriched uranium into a powder for a medical research reactor that is difficult to reprocess for weapons production, experts and UN monitors say.

The work, noted in a technical report by the UN's nuclear watchdog agency in late August, suggests Iran is trying to display enough goodwill to restart nuclear talks with world powers, while aiming to soften demands by the United States and others to halt Tehran's top-level uranium enrichment.

An influential Iranian parliament member, Hossein Naqavi, said the country was taking a "serious and concrete confidence-building measure" by converting some of the 20 percent enriched stockpile into U3O8, or uranium oxide, in the form of powder.

The move also appears to be part of a wider strategy to seek relief from tightening Western sanctions, in exchange for step-by-step plans to scale back uranium enrichment.

But Iran has offered no substantial concessions to cut into its stockpile of 20 percent enriched uranium, the highest level acknowledged by the Islamic Republic.

Iran's 20 percent enrichment program is among the core disputes. That's because it can be boosted to weapons-grade far more rapidly than the 3.5 percent-enriched uranium used for Iran's lone energy reactor.

The United States and its allies want Iran to halt the 20 percent production and ship the rest of the material out of the country.

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